LONGUS PILUS OF ENTEROTOXIGENIC ESCHERICHIA-COLI AND ITS RELATEDNESS TO OTHER TYPE-4 PILI - A MINIREVIEW

Longus is a long pilus produced by human enterotoxigenic Escherichia c oli (ETEC) which shares significant structural and biochemical feature s with class-B type-4 pili. These pili include the toxin-coregulated p ilus (TCP) of Vibrio cholerae, the bundle-forming pilus (BFP) of enter opathogenic E. coli and both longus and the colonization factor antige n III (CFA/III) of ETEC. These pili are produced under defined growth conditions indicating that they are under the control of different reg ulatory elements. While TCP is chromosomally encoded, the remaining pi li are encoded on large virulence plasmids. Longus and CFA/III are clo sely related pili although certain DNA and protein differences also ex ist between them. This may account for the differences in the regulati on, surface presentation, antigenicity, and prevalence of these two pi lins among ETEC. Neighboring lngA, a second open reading frame termed lngB was found which encodes a protein with significant homology to pr oteins which are part of a type-II secretory system such as XcpV, OutC , and PulO of Pseudomonas aeruginosa, Erwinia chrysanthemi, and Klebsi ella pneumoniae, respectively. This suggests that lngB may be an acces sory gene involved in biogenesis of longus. (C) 1997 Elsevier Science B.V.